The Tetens equation is an equation to calculate the saturation vapour pressure of water over liquid and ice. It is named after its creator, O. Tetens who was an early German meteorologist. He published his equation in 1930,
[Tetens, O. 1930. Über einige meteorologische Begriffe. Z. Geophys 6: 297-309.] and while the publication itself is rather obscure, the equation is widely known among meteorologists and climatologists because of its ease of use and relative accuracy at temperatures within the normal ranges of natural weather conditions.
The equation is structurally identical to the
August-Roche-Magnus equation, but the coefficients differ.
Formula
Monteith and Unsworth (2008) provide Tetens' formula for temperatures above 0 °C:
[Monteith, J.L., and Unsworth, M.H. 2008. ''Principles of Environmental Physics''. Third Ed. AP, Amsterdam. http://store.elsevier.com/Principles-of-Environmental-Physics/John-Monteith/isbn-9780080924793/]
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where temperature is in
degrees Celsius
The degree Celsius is the unit of temperature on the Celsius scale (originally known as the centigrade scale outside Sweden), one of two temperature scales used in the International System of Units (SI), the other being the Kelvin scale. The ...
(°C) and saturation vapor pressure is in
kilopascal
The pascal (symbol: Pa) is the unit of pressure in the International System of Units (SI), and is also used to quantify internal pressure, stress, Young's modulus, and ultimate tensile strength. The unit, named after Blaise Pascal, is defined a ...
s (kPa). According to Monteith and Unsworth, "''Values of saturation vapour pressure from Tetens' formula are within 1 Pa of exact values up to 35 °C.''"
Murray (1967) provides Tetens' equation for temperatures below 0 °C:
[Murray, F.W. 1967. On the computation of saturation vapour pressure. J. Applied Meteorology 6: 203-204. https://doi.org/10.1175/1520-0450(1967)006%3C0203:OTCOSV%3E2.0.CO;2]
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See also
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Vapour pressure of water
The vapour pressure of water is the pressure exerted by molecules of water vapor in gaseous form (whether pure or in a mixture with other gases such as air). The saturation vapour pressure is the pressure at which water vapour is in thermodynamic ...
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Antoine equation
The Antoine equation is a class of semi-empirical correlations describing the relation between vapor pressure and temperature for pure substances. The Antoine equation is derived from the Clausius–Clapeyron relation. The equation was presented ...
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Arden Buck equation The Arden Buck equations are a group of empirical correlations that relate the saturation vapor pressure to temperature for moist air. The curve fits have been optimized for more accuracy than the Goff–Gratch equation in the range .Buck 1981
A s ...
*
Lee–Kesler method
The Lee–Kesler method
allows the estimation of the saturated vapor pressure at a given temperature for all components for which the critical pressure ''P''c, the critical temperature ''T''c, and the acentric factor ''ω'' are known.
Equation ...
*
Goff–Gratch equation The Goff–Gratch equation is one (arguably the first reliable in history) amongst many experimental correlation proposed to estimate the saturation water vapor pressure at a given temperature.
Another similar equation based on more recent data is ...
References
{{Reflist
Meteorological concepts
Thermodynamic equations